Graduation Year

2024

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Electrical Engineering

Major Professor

Arash Takshi, Ph.D.

Co-Major Professor

Sylvia Thomas, Ph.D.

Committee Member

Stephen Saddow, Ph.D.

Committee Member

Ryan Toomey, Ph.D.

Committee Member

Ajeet Kaushik, Ph.D.

Keywords

String Electrodes, Electrochemical Biosensors, PVDF Nanofibers, PEDOT:PSS Thin Film, Organic-Polymer Material Interfacing, Stretchable Electric Double Layer Capacitors

Abstract

As progress in the field of nanotechnology continues to evolve, it is becoming more and more prevalent to apply this small but powerful technology to portable wearable electronics. The unique scale of such a technology lends its expertise to the investigation of enzymes for biometric related diagnostics or in the development of light weight flexible energy storage devices. Furthermore, as the need for highly precise and durable wearable electronics grows, the next generation of electronics must keep pace with this development in terms of shape, flexibility, functionality, and performance.

The presented research reviews the current state of art of nanofiber technology as it relates to energy storage and biosensing capabilities of nanofiber technology. Following that the unique structure and nature of the Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibers have been explored at length and its beneficial partnership with the conductive polymer Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) has been studied. Further exploration into the respective polymers' characteristics and interactions with synthetic and non-synthetic materials have been explored to further the understanding in polymer interfacing with biological and ionic liquid solutions.

The aim of this research was to design, fabricate, and electrochemically characterize fiber-based electrodes for biosensors and energy storage devices. This research was accomplished by outlining 4 main objectives to guide this work. First, the study of polymers for conductive flexible wearable electrode development was explored. This study can be seen in chapter 2 where the polymers used throughout this research are observed and compared to current state of art works. Second, the implementation and subsequent study of the feasibility of bioprinting a conductive polymer based electrochemical storage cell was conducted. The results of which are seen in chapter 3 as the bioprinted electrodes utilizing the PEDOT:PSS polymer was assembled in a parallel two terminal electric double layer supercapacitor design. Which while unique in approach, the results proved limited due to the hydrophilic nature of the electrochemical cell. That research led into the third guiding objective which was to design and study a nanofiber-based string electrode for wearable biosensors. This objective was created as a result of the exploration of conductive polymers studied during the completion of the first and second guiding objectives. The results of this objective can be seen in chapters 5 and 6. Given the fluctuating nature of the bioprinting approach of the conducting polymers the implementation of nanofiber technology as an alternative flexible base electrode was applied. When implemented the resulting enhanced surface area to the electrode demonstrated improved performance and mechanical stability to the electrode overall. Lastly, upon successful analysis of the nanofiber-based string electrode, fabricated from the third guiding objective, it was applied for wearable energy storage devices and tunable biosensor applications for further investigation into the use of this novel technology. The results of this can be seen in chapters 4 and 7. Moreover, the research described in this work provides a scientific contribution as it clearly outlines the development of a flexible/stretchable nanofiber-based string electrode for a potential use in tunable biosensor and stretchable energy storage wearable devices.

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